Scientific and Technical Information (STI)
From the “about” page:
STI (scientific and technical information) is the collected set of facts, analyses, and conclusions resulting from scientific, technical, and related engineering research and development efforts, both basic and applied.
That has to be a classic as far as non-helpful explanations. 😉
Or you can try:
This site helps you locate, obtain, and publish NASA aerospace information and find national and international information pertinent to your research and mission.
A little better.
Access publicly available NASA and NACA reports, conference papers, journal articles, and more. Includes over a quarter-million full-text documents, and links to more than a half-million images and video clips.
Better still.
And then:
NTRS promotes the dissemination of NASA STI to the widest audience possible by allowing NTRS information to be harvested by sites using the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH). OAI-PMH defines a mechanism for information technology systems to exchange citation information using the open standards HTTP (Hypertext Transport Protocol) and XML (Extensible Markup Language). NTRS is designed to accept and respond to automated requests using OAI-PMH. Automated requests only harvest citation information and not the full-text document images.
Which means you can populate your topic map with data from this source quite easily.